1. Field of the Invention
The present invention relates to an apparatus and method for orienting a semiconductor wafer or the like during manufacturing or testing processes for the semiconductor device. In the apparatus and method of the invention, the wafer is positioned relative to a notched portion formed on a part of the wafer in preparation of subsequent processing operations.
2. Description of the Prior Art
When semiconductor wafers are subjected to work or measure processing, the wafers are usually put in a rack-shaped cassette and taken out one by one from the cassette by a conveyance apparatus and held on the stage of a processing apparatus. The position of a notched portion of a wafer within the cassette is random, and in the processing apparatus, since positioning is carried out with respect to a notched portion on an edge of the wafer, the wafer must be held on the stage so that the notched portion is at a definite position (e.g., a definite position in the front of the stage).
Therefore a wafer taken out from the cassette is first held on a positioning apparatus by the conveyance apparatus, transferred to the correct position with respect to the notched portion of the wafer and then held on the stage of the processing apparatus.
Positioning apparatuses used in such processes in the prior art generally have structures wherein a wafer is rotatably supported. A rubber roller is pushed to a circumferential edge portion of the wafer and is then rotated and driven. The wafer is thereby rotated, and when a notched portion of the wafer reaches a portion of the rubber roller or a portion of an optical sensor or the like, rotation of the wafer is stopped and the wafer is positioned (refer to, e.g., JPA No. 16984/1979).
However, when the wafer is positioned in this manner, since the circumferential edge portion of the wafer is rotated while being pushed by the rubber roller or is moved contacting with another member, the circumferential edge portion of the wafer may become weak and thus flawed.
Consequently, the present inventor has proposed through JPA No. 138957/1991 a positioning apparatus wherein a circumferential edge portion of a wafer does not contact with any other member such as a roller, while the position of the wafer can be safely and correctly positioned with respect to a notched portion.
In this positioning apparatus, however, a problem exists in that although the wafer can be positioned in a non-contact state safely and correctly with respect to the notched portion, many operations are necessary and a considerable amount of time is required to some degree for the positioning. In particular, during the positioning operation, first, a wafer inserting part is reciprocated and moved in an X-axis direction and the center positions of the wafer and the wafer inserting part are aligned relative to the X-axis. Next, the wafer inserting part is reciprocated and moved in a Y-axis direction and the center positions of the wafer and the wafer inserting part are aligned relative to the Y-axis. Finally the wafer held on the center position of the rotary part is rotated, and the position of the notched portion is detected. This operation is carried out so that the notched portion is positioned to a prescribed angle position of the notched portion.